[asterisk-dev] [Code Review] 2756: Fix deadlocks in chan_sip in REFER and BYE handling

[Mark Michelson]

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trunk/channels/chan_sip.c
<https://reviewboard.asterisk.org/r/2756/#comment18453>

    Grab a reference to transferer->owner before unlocking transferer. This way, you can guarantee not to pass an invalid pointer into ast_channel_bridge_peer().



trunk/channels/chan_sip.c
<https://reviewboard.asterisk.org/r/2756/#comment18455>

    Like with your previous case, get a reference to p->owner before unlocking p.
    
    Since this is the exact same sequence as the previous case where the bridged peer is acquired, I think it should exist as its own function.
    
    Since this case also then uses the same deadlock avoidance technique in order to lock the bridged peer, I think the function you create should also try to return with all components (sip_pvt, sip_pvt's owner, bridged peer) locked.


- Mark Michelson


On Aug. 12, 2013, 3:51 p.m., opticron wrote:
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> This is an automatically generated e-mail. To reply, visit:
> https://reviewboard.asterisk.org/r/2756/
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> 
> (Updated Aug. 12, 2013, 3:51 p.m.)
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> 
> Review request for Asterisk Developers and Mark Michelson.
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> Bugs: ASTERISK-22215
>     https://issues.asterisk.org/jira/browse/ASTERISK-22215
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> Repository: Asterisk
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> Description
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> This resolves several deadlocks in chan_sip relating to usage of ast_channel_bridge_peer and improves accessibility of lock debugging function calls.
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> These issues were found while fixing the sip attended transfer integration tests for the referenced bug.
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> Diffs
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>   trunk/channels/chan_sip.c 396504 
>   trunk/include/asterisk/lock.h 396504 
>   trunk/main/utils.c 396504 
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> Diff: https://reviewboard.asterisk.org/r/2756/diff/
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> Testing
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> With these changes, chan_sip no longer stalls part of the way through the rewritten sip attended transfer tests on the REFER or at the end on the final BYE.
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> Thanks,
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> opticron
> 
>

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